Nitrogen-rich metal-organic framework for CO2 capture

https://doi.org/10.1038/srep01149

“The high porosity and stability together with the coordination-free triazole moieties and open metal sites are favorable to the interactions between gas molecules and the framework of NTU-105, which inspired us to investigate its gas uptake capacity and selectivity towards CO₂. As shown in Figure 3, CO₂ sorption isotherms reveal an uptake capability of NTU-105 as high as 187 cm³ g⁻¹ (36.7 wt%) at 1 atm and 273 K, which makes NTU-105 a top MOF material for CO₂ uptake reported to date^17,18, including its isoreticular MOFs containing acylamide groups, amine units, or triazine moieties (i.e., 42.6% for Cu-TPBTM³⁹ and 44.5% for Cu-TDPAT⁴¹). For comparison, the N₂ uptake of NTU-105 at 273 K and 1 atm was measured to be only 16 cm³ g⁻¹. The high adsorption selectivity of NTU-105 towards CO₂ over N₂ under the same conditions (Figure 3) indicates that NTU-105 is highly applicable in the separation of CO₂ over N₂. Then, the isosteric heat of adsorption (Q_st) for CO₂ was calculated based on the adsorption isotherms at different temperatures (273 and 298 K, Figure S11 in the SI) through Clausius-Clapeyron equation¹⁷. It was found that Q_st is ~35 kJ mol⁻¹ at low loading range, followed by the convergence into a pseudo-plateau (~24 kJ mol⁻¹) with relatively high uptake, the observations which are indicative of strong CO₂-framework interactions. The Q_st value at low loading range is the second highest one among the reported rth-MOFs, while Cu-TDPAT presents the highest value (42.2 kJ mol⁻¹) so far⁴¹.”